Ezra Klein and I are engaged in a little debate over the value of organic food. I’m honestly a little surprised to be arguing with the Washington Post’s food-policy columnist about the desirability of removing toxic, ecologically damaging chemicals from food production. But no matter.

I say they almost certainly do; Ezra is skeptical. From reading Ezra’s post and several comments from his readers, I find that people seem downright nonplussed by the idea that soil conditions and growing methods might affect the nutritional content of the resulting food. Their puzzlement in turn puzzles me. If we are what we eat, then so are plants; and plants are mainly eating soil (and the various nutrients and substances contained therein).

It makes me wonder what–or if?–people in our post-agricultural society think about the whole question of soil. Yet methods of soil stewardship are key to this debate. So before I dig into the details with the celebrated policy wonk–which study says what, funded by whom–I want to take a broad look at soil. In the process, I hope to open people’s minds to the idea that soil stewardship could affect food quality.

In his In Defense of Food, Michael Pollan pretty much debunked the tenets of what he called “nutritionism”–the idea that human nutrition could be reduced to a set of macronutrients (vitamin A, the B vitamins, etc.), which could then be isolated and fed to be people to keep them healthy. Scientists have known for a while that a given dose of, say, isolated vitamin A in pill form (or added to bread as fortification) does not provide anything close to the same benefit as an equal dose in the context of a carrot. You can’t live well on 2,500 calories from sugar water plus oat fiber and a One a Day vitamin. Scientists now know that, but haven’t quite figured out why. Human nutrition turns out to be more mysterious than people in white lab coats have so far been able to decipher.

For about 100 years now, a form of nutritionism has also held sway among soil scientists, too. Where human nutritionists focused on vitamin A, etc., soil scientists seized upon N, P, and K–nitrogen, phosphorous, and potassium. No one disputes that these are basic building blocks of plant life–without sufficient access to each of them, plants can’t flourish. But just as human nutritionists at one time thought that nutrition could be isolated into macronutrients and delivered to people out of the context of food, so plant scientists decided that N, P, and K were sufficient, in isolated form, for plant life.

This idea marked the rise of what become known as NPK thinking–the nutritionism of soil scientists. By learning to synthesize nitrogen and mine phosphorous and potassium, technologists sparked an agricultural revolution. Farmers could abandon the time-consuming task of recycling nutrients and building soil; instead, they could merely purchase newly available inputs (on the installment plan, of course). Society had “solved” the whole vexing problem of soil fertility; farmers could now focus on growing food, and lots of it (meaning fewer farmers).

In the NPK-think that still rules conventional agriculture, soil is essentially an inert medium for conveying isolated blasts of synthesized and mined NPK to crops. The effect on soil quality has been dreadful. Writing in The Fatal Harvest Reader (2002), the California farmer Jason McKenney describes the effect:

We now know that massive use of synthetic fertilizers to create artificial fertility has had a cascade of adverse effects on natural soil fertility and the entire soil system. Fertilizer application begins the destruction of soil biodiversity by diminishing the role of nitrogen-fixing bacteria and amplifying the role of everything that feeds on nitrogen. These feeders then speed up the decomposition of organic matter and humus. As organic matter decreases, the physical structure of soil changes. With less pore space and less of their sponge-like qualities, soils are less efficient at storing water and air. More irrigation is needed. Water leeches through soils, draining away nutrients that no longer have an effective susbstrate on which to cling. With less available oxygen the growth of soil microbiology slows, and the intricate ecosystem of biological exchanges breaks down.

I saw it in extreme form on a trip last spring to Immokalee, Florida–source of 90 percent of the winter tomatoes grown in the United States. As I and many others have pointed out, workers are abused there as a matter of course.

But the growing conditions are also quite startling. When you look down in an Immokalee tomato field, what you see is sand–there’s no evident organic matter in the growing medium (the word “soil” doesn’t quite apply here). To prepare for tomato growing, you start by sterilizing the ground with an extremely toxic pesticide–and in the process wipe out any beneficial microbes that might be lingering there. Then you inject the doses of NPK to maximize output, and you’re ready to go. (You may need more insecticide sprayings as the season wears on.)

More than in any other place I’ve seen, plants there live on a diet equivalent to sugar water, oat fiber, and vitamin pills. Can there be any real wonder that the resulting tomatoes are so pathetically lacking in flavor? And do people still doubt that they may be less healthful as well?

In contrast to industrial agriculture’s reliance on NPK, organic ag focuses on building soil as a living ecosystem. Even large-scale industrial-organic farms nourish their soil with nitrogen-fixing cover crops and well-composted manure, which along with NPK deliver loads of organic matter and micronutrients. And the nitrogen available from legume cover crops and manure releases slowly, not jolting crops into rapid growth like straight anhydrous ammonia. And whereas the harsh chemicals and poisons of conventional farming squeeze out microbial life in the soil, organic farmers seek to nourish it.

Given all of this, I would be surprised if a tomato grown in Immokalee’s chemical-infused sands delivered as much health-giving properties as one grown in rich, living humus.

All right, so back to the details of the debate.

I pointed to a literature review conducted by the U.S.-based Organic Center, which is funded by Big Organic groups like Horizon and Whole Foods; Ezra pointed to one funded by the U.K. Food Safety Agency, the equivalent of the U.S. FDA. And like that agency, the FSA has not managed to remain free of food-industry influence. For example, its current chief executive is Tim Smith, whose bio reads like this:

Tim Smith is the former Chief Executive of Arla Foods UK plc. The company, which is responsible for a number of major food brands, is now part of Arla Foods amba, Europe’s largest dairy manufacturer. He was appointed Chief Executive of Arla Foods in early 2005.

Tim Smith graduated from Leeds University with a degree in microbiology and zoology. He has spent his entire career in the food business: from 1979 to 1994 he was at Northern Foods, finishing his career there as a Divisional Director. After five years at Sara Lee Corporation, where he was President of UK operations, he joined Express Dairies plc as Executive Director. Express Dairies merged with Arla Foods in October 2003.

Impressive. I don’t think even a U.S. president would appoint a career Big Food exec to the top food-safety post upon his first swing through the revolving door. Even Michael Taylor, the former Monsanto exec (and before that, lawyer) Obama recently handed a top position at FDA, served a few stints in government before the appointment.

At any rate, neither Ezra nor I is leaning on a pristine study untainted by special interest. And in this age of industry dominance of research agendas, there may be no pristine studies. So let’s look at details.

Ezra makes two major points to refute my position: 1) organic food may have more total antioxidants than conventional, but that’s irrelevant, because of the “wealth of studies showing that antioxidants do not appear to reduce the risk of cancer or heart disease or anything else”; and 2) that my contention that the lower nitrogen content of organic foods makes them healthier is based on a “circumstantial argument” about the danger of nitrates “that is plausible, but hasn’t been studied.”

Ezra links to two studies to back up his claim about the irrelevance of antioxidants. The first one is itself irrelevant, because it is measuring the value of antioxidant supplements–ie, isolated antioxidants–and we’re talking about antioxidants in whole foods. I agree that taking, say, beta-caratene pills is probably worthless; I doubt that beta-caratene in, say, the context of a carrot is worthless.

The second study is more interesting. This investigates whether “natural antioxidants, i.e. Vitamin C, Vitamin E and carotenoids” fight certain kinds of heart damage. It concludes:

Animal studies indicate that dietary antioxidants may reduce atherosclerosis progression, and observational data in humans suggest that antioxidant vitamin ingestion is associated with reduced cardiovascular disease, but the results of randomised controlled trials are mainly disappointing.

I assume that by “dietary antioxidants,” the researchers mean nutrients from whole foods and not isolated supplements. So the finding would seem to support Ezra’s claim. But then we get this:

The favourable effects shown by some studies relating antioxidant dietary intake and cardiovascular disease, may have been exerted by other chemicals present in foods. Flavonoids are the ideal candidates, since they are plentiful in foods containing antioxidant vitamins (i.e. fruits and vegetables) and are potent antioxidants. Tea and wine, rich in flavonoids, seem to have beneficial effects on multiple mechanisms involved in atherosclerosis.

So flavonoids may actually help, according to this study. Now, both the FSA and Organic Center studies measured something called “total phenolics,” a category than encompasses flavonoids. The FSA study found no difference; and the Organic Center study showed a more than 20 percent advantage for organic food. Both studies are essentially gathering results from past studies and consolidating their results. As such, they’re looking at much the same data. So why the difference? According to the Organic Center’s critique of the FSA study:

Unlike the London study, The Organic Center review focused on nutrient differences in “matched pairs” of crops grown on nearby farms, on the same type of soil, with the same irrigation systems and harvest timing, and grown from the same plant variety. It also rigorously screened studies for the quality of the analytical methods used to measure nutrient levels, and eliminated from further consideration a much greater percentage of the published literature than the FSA team.

While the FSA team found 80 comparisons of phenolic compounds, the TOC [Organic Center] team focused on the more precise measure of total phenolic acids, or total polyphenols, and found just 25 scientifically valid “matched pairs.” By mixing together in their statistical analysis the results of several specific phenolic acids, the FSA team likely lost statistical precision.

The “matched pairs” thing seems legit. Crops draw nutrients from soils; different soils have different levels and types of nutrients. Different vegetable varieties, too, have different properties–including levels of nutrient uptake.

At the University of California-Davis, scholars at the Long Term Research on Agricultural Systems project have been examining “matched pairs” of organic and conventional crops since 1993. In a 2007 paper, the group compared the nutritional content of organic and conventional tomatoes grown between 1994 and 2004. The result: organic tomatoes showed significantly levels of two flavonoids called quercetin and kaempferol that were on average, respectively, 79 percent and 97 percent higher than conventional. Moreover:

The levels of flavonoids increased over time in samples from organic treatments, whereas the levels of flavonoids did not vary significantly in conventional treatments. This increase corresponds not only with increasing amounts of soil organic matter accumulating in organic plots but also with reduced manure application rates once soils in the organic systems had reached equilibrium levels of organic matter.

Okay, on to the question of nitrogen. As I wrote in the earlier post, both the FSA and Organic Center studies acknowledge that organic foods show lower levels of nitrogen in organic food. I cited that fact as a serious nutritional advantage for organic food, and pointed to a recent study by a Brown researcher linking type-2 diabetes and Alzheimer’s disease to increased exposure to nitrogen-related compounds.

Ezra dismissed the argument as “circumstantial.”

I should have been more precise. As the Organic Center put it in its rebuttal to the FSA, “Elevated levels of nitrogen in food are regarded by most scientists as a public health hazard because of the potential for cancer-causing nitrosamine compounds to form in the human GI tract.”

And it’s nitrosamine compounds that the Brown study linked to diabetes and Alzheimer’s. The researcher makes a circumstantial link between the explosion in nitrogen fertilizer applications after 1960 and the abrupt rise in Alzeimer’s and diabetes over the same period. But they also demonstrate the ability of nitrosamines to cause significant cellular damage. According to the study’s press release:

Nitrosamines basically become highly reactive at the cellular level, which then alters gene expression and causes DNA damage. The researchers note that the role of nitrosamines has been well-studied, and their role as a carcinogen has been fully documented. The investigators propose that the cellular alterations that occur as a result of nitrosamine exposure are fundamentally similar to those that occur with aging, as well as Alzheimer’s, Parkinson’s and Type 2 diabetes mellitus.

Given that information, it seems wise to minimize the level of nitrogen–which can turn to nitrosamines in the digestive process–in food. Moreover, the researchers evidently aren’t finished with the topic. The press release adds, chillingly: “Two subsequent papers have been accepted for publication in the near future that demonstrate experimentally that low levels of nitrosamine exposure cause neurodegeneration, NASH [non-alcoholic steatohepatitis], and diabetes.”

Nor are these the only ways that organics are “better for you.” Here’s an important one: they carry drastically lower pesticide residues. The Chicago Tribune recently obtained USDA data showing that “more than 50 pesticide compounds showed up on domestic and imported peaches headed for U.S. stores.” Moreover:

Five of the compounds exceeded the limits set by the Environmental Protection Agency, and six of the pesticide compounds present are not approved for use on peaches in the United States.

Ezra ended his response like this: “[W]hat we do know is that organic produce is more expensive and harder to find.”

I agree completely; but it seems clear to me that the answer is not to marginalize organics, but rather to stop using government cash and lax antitrust/environmental/labor regulation to prop up a destructive food system. We get the food system that we as a society pay for.